Piezoelectric ceramic compositions principally containing lead zirconate titanate (Pb(Ti, Zr)O3, hereinafter referred to as “PZT”) have excellent piezoelectric properties and therefore are widely used for piezoelectric devices such as piezoelectric actuators.
In general, the properties required for the piezoelectric ceramic compositions include a large piezoelectric constant, a small dielectric constant and a high Curie point, and the like.
In order to enhance properties of the piezoelectric ceramic compositions containing PZT, the B site components Ti and Zr are replaced with another atom in such a manner that PZT is doped with Pb(Ni1/3Nb2/3)O3 (hereinafter referred to as “PNN”), Pb(Zn1/3Nb2/3)O3 (hereinafter referred to as “PZN”), and/or the like.
For example, Patent Document 1 discloses a quaternary piezoelectric ceramic material represented by the composition formula PbA[(Zn1/3Nb2/3)W(Ni1/3Nb2/3)XTiYZrZ]O3, wherein W+X+Y+Z=1, 0.985<A≦0.995, 0.10≦W+X≦0.70, 0.20≦Y≦0.50, and 0.10≦Z≦0.50.
In addition to such a quaternary composition, the A site component Pb is replaced with another element such as Ca, Sr or Ba such that properties are enhanced.
For example, Patent Document 2 discloses a piezoelectric ceramic composition represented by the composition formula PbA[(Zn1/3Nb2/3)W(Ni1/3Nb2/3)XTiYZrZ]O3, wherein W+X+Y+Z=1, 0.960≦A≦0.985, 0≦W≦0.70, 0≦X 0.50, 0.25≦W+X≦0.70, 0.20≦Y≦0.40, 0.057≦Z≦0.375, where up to five mole percent of Pb is replaced with at least one of Ca, Sr, and Ba.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 11-322422
Patent Document 2: Japanese Unexamined Patent Application Publication No. 60-103079